Abstract: 【Objectives】 An eight consecutive year (2005-2012) field experiment was conducted to evaluate tillage practices on soil organic carbon, microbial biomass and soil enzyme activity and their distributions in 0-90 cm depth of soils in arid northwestern China, to which would provide a theoretical basis for better choosing tillage practices. 【Methods】The treatments include permanent raised bed (PRB), zero tillage with control traffic on flat field (PFT) and conventional tillage (CT), and the total soil organic carbon(TOC), particulate organic carbon(POC), microbial biomass carbon(MBC), microbial biomass nitrogen(MBN), microbial biomass phosphorus(MBP), enzymatic activities (invertase, urease and catalase) and grain yield of spring wheat were measured. 【Results】The contents of TOC, POC, MBC, MBN and MBP and the activities of invertase and urease were declined with increasing depth (0-90 cm) in the PRB, PFT and CT treatments, and the catalase activity was decreased first and then increased. In the whole 0-60 cm soil depth, the SOC storage was the highest under PRB, followed by the PFT and CT treatments in crop growth areas. The activities of enzymes (invertase and urease) and the contents of TOC, POC, MBC, MBN and MBP in the upper layer (0-10 cm) in the plots tilled by PRB and PFT were higher than those in the plots tilled by CT. There were significant and extremely significant correlations among TOC, POC, MBC, MBN, MBP and enzyme activities (invertase, urease and catalase), while the catalase activity was not significantly affected by the three tillage modalities. 【Conclusions】The PRB and PFT treatments could improve the contents of soil organic carbon, microbial biomass, soil enzyme activities and the grain yield, and the sequestration of carbon in the whole profile of 60 cm under the PRB treatment was greater than that under the CT and PFT treatments. Beneath 10 cm, there was no significantly improvement in soil environment for the PRB and PFT treatments compare with the CT treatment.